It is a known procedure to secure fold-down backrests of motor vehicle seats to the car body in such a way that they can be unlocked. The state of the art discloses approaches in which the moveable backrest can be operated by a vehicle user and can be detached from the car body either manually or by means of actuators. The manual or automatic locking devices needed for this purpose are, for the most part, arranged at the side of the backrest. Such locking devices that are arranged at the side of the backrests of motor vehicle seats and that serve either only to fold down the backrest or else to fold down as well as to adjust the inclination of the backrest are the subject matter of several publications.
Manual locking and inclination-adjustment devices can be gleaned from various publications.
German patent application DE 195 40 390 A1 discloses a vehicle seat having a manually operated holding device for affixing a vehicle backrest to the car body. Holding elements are configured on the backrest and on the car body in order to allow a limited adjustment capability of the backrest inclination relative to the seat cushion while, at the same time, securing the backrest to the car body. The positioning of the backrest relative to the seat cushion can be freely selected within certain limits.
German patent application DE 30 45 309 A1 describes another manually operated assembly for the back seat of a motor vehicle, with a backrest that can be folded down towards the front and that is held near its upper end on the car body by means of a pin and a latching means that interacts with the pin. The pin can be moved—with the backrest or with a guide element that is attached to the car body—parallel to itself approximately in the lengthwise extension of the vehicle, and it can be joined to the latching means present on the car body or on the backrest in several positions that result in several different angular positions for the backrest.
Automatically driven locking and/or inclination-adjustment devices can likewise be gleaned from several publications.
German patent application DE 43 16 567 A1 describes an automatically driven inclination-adjustment device for a backrest. This document discloses a vehicle seat comprising a seat part to whose lower end a pivotable backrest is hinged. A pivoting range is attained for the backrest in that an actuator operated by an electric motor and arranged on a pillar engages with the backrest at a distance from the pivoting axis of the backrest and executes the pivoting movement of the backrest.
Another automatically operated inclination-adjustment device for a backrest is disclosed in German patent application DE 102 09 759 A1. A vehicle seat or a back seat comprises a seat part and a backrest, both of which have a fold-down function effectuated by an electric drive, whereby the fold-down function causes the backrest or a part of the backrest to fold down relative to the seat part. The fold-down function is realized in that the electric drive has an inclination-adjustment function, whereby the adjustment speed of the electric drive can be varied in such a way that a different speed can be set for the inclination-adjustment function and for the fold-down function.
Moreover, a combined capability for locking and unlocking as well as for electrically adjusting the inclination of a backrest is disclosed in German patent specification DE 199 26 839 C1. This patent document describes an inclination-adjustment device having a bracket-like receptacle that is connected to a backrest, especially at its upper end, so that it can pivot by means of a laterally arranged locking pawl. Here, releasing this locking pawl allows not only for the inclination to be adjusted but also for the backrest to be folded down.
German patent application DE 10 2008 064 523 A1 discloses another locking-adjustment arrangement for locking and adjusting a fold-down backrest of a seat of a motor vehicle by means of a drive means. The locking-adjustment arrangement for locking and adjusting a pivotable backrest has a locking-adjustment device that is attached to the car body and that comprises a locking element as well as a lock situated on the backrest. Here, the locking-adjustment device has a support part that interacts with a drive spindle and that supports the locking element, and it also has a drive means, so that the inclination of the backrest that is connected to the locking element can be adjusted by means of the locking element that is operatively connected to the drive means.
It has been found in actual practice that the approaches involving a drive are very convenient in terms of adjusting the inclination. However, they are relatively complex and consequently expensive, in addition to which two drives are, in fact, needed—especially in the case of multi-part backrests having multiple sections—so that the inclination of the parts of a two-part backrest can be adjusted automatically and separately. For this reason, there continues to be a great need for manual locking and adjustment assemblies that are not only inexpensive but also as convenient as possible. In this context, the invention is based on certain preconditions which a new manual locking and adjustment assembly is supposed to meet. A first precondition is that only a small amount of effort should be involved in the production of a locking and adjustment assembly as far as the car body is concerned. A second precondition is that the backrest inclination should be adjustable and also that it should be possible to unlock the backrest to fold it down onto the seat part. A third precondition pertains to the safety of the locking and adjustment assembly. The backrest should always remain in a secured state during the inclination adjustment, so that the inclination can be adjusted without this allowing the backrest to be freely movable relative to the car body. At least one of these preconditions is not met by the locking and adjustment arrangements known from the state of the art.